2008/06/25 by Ji-Wei Xie, Ji-Lin Zhou · 43 citations
Physics and Astronomy · #Accretion (finance) #Accretion disc #Astro and Planetary Science #Astrophysics and Star Formation Studies #Binary number #Dissipation #Drag #Mass ratio #Orbital elements #Perturbation (astronomy) #Planet #Planetesimal #Stellar, planetary, and galactic studies #astro-ph #astro-ph.EP
paper · pdf · doi:10.1088/0004-637x/698/2/2066
published in The Astrophysical Journal 698(2), 2066-2074 (IOP Publishing) · 9 pages, 6 figures, ApJ, 698, 2066
openalex publication_date 2009/06/08 · arxiv created 2009/06/09 · arxiv updated 2015/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Recent observations show that planets can reside in close binary systems with stellar separation of only ∼20 AU. However, planet formation in such close binary systems is a challenge to current theory. One of the major theoretical problems occurs in the intermediate stage—planetesimals accretion into planetary embryos—during which the companion's perturbations can stir up the relative velocities (▵ V ) of planetesimals and thus slow down or even cease their growth. Recent studies have shown that conditions could be even worse for accretion if the gas-disk evolution was included. However, all previous studies assumed a two-dimensional disk and a coplanar binary orbit. Extending previous studies by including a three-dimensional gas disk and an inclined binary orbit with small relative inclination of i B = 0 1–5°, we numerically investigate the conditions for planetesimal accretion at 1–2 AU, an extension of the habitable zone (∼1–1.3 AU), around α Centauri A in this paper. Inclusion of the binary inclination leads to the following: (1) differential orbital phasing is realized in the three-dimensional space, and thus different-sized bodies are separated from each other, (2) total impact rate is lower, and impacts mainly occur between similar-sized bodies, (3) accretion is more favored, but the balance between accretion and erosion remains uncertain, and the "possible accretion region" extends up to 2 AU when assuming an optimistic Q * (critical specific energy that leads to catastrophic fragmentation), and (4) impact velocities (▵ V ) are significantly reduced but still much larger than their escape velocities, which infers that planetesimals grow by means of type II runaway mode. As a conclusion, the inclusion of a small binary inclination is a promising mechanism that favors accretion, opening a possibility that planet formation in close binary systems can go through the difficult stage of planetesimals accretion into planetary embryos.